POS0281 SAFETY OF BIOSIMILARS THERAPIES FOR THE TREATMENT OF JUVENILE IDIOPATHIC ARTHRITIS: RESULTS FROM THE SPANISH REGISTRY OF ADVERSE EVENTS WITH BIOLOGIC THERAPIES (BIOBADASER)
Authors: J. J. Bethencourt Baute, L. Otero-Varela, F. J. Manero Ruiz, E. Perez-Pampín, C. Rodríguez-Lozano, S. Manrique Arija, S. Bustabad, C. Fernández-López, D. Ruiz Montesinos, L. Mateo, R. Martín-Domenech, M. Moreno, F. Sánchez-Alonso, I. Catrejón
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease in childhood. The treatment of JIA has been revolutionized by the use of biologic agents. The use of biosimilar disease modifying antirheumatic drugs (bsDMARD) therapy in young adults is not well studied, therefore more evidence regarding drug safety is needed. <h3>Objectives</h3> Our aim is to assess the safety of bsDMARD therapy in JIA. <h3>Methods</h3> Data was obtained from BIOBADASER, a multicenter prospective registry based on routine clinical practice. All patients diagnosed before age 16 in our database between 2000 and 2022 were included in the analysis. JIA is classified into 7 subgroups: systemic, persistent or extended oligoarthritis, RF positive polyarthritis, RF negative polyarthritis, enthesitis-related arthritis, psoriatic arthritis, and undifferentiated arthritis. Due to the registry design, it was not possible to identify each of the JIA subgroups; thus, we classified them into oligo/polyarticular JIA, JIA related to enthesitis, and psoriatic JIA. Adverse events were coded using version 13.0 MedDRA (Medical Dictionary for Regulatory Activities). Proportions, means and standard deviations (SD) were used to describe our population. Incidence rates (IR) of adverse events and 95% confidence intervals were calculated, and Poisson regression was used to estimate incidence rate ratios (IRR), adjusting by sex, diagnosis type, age at start of therapy (≤16 years vs &gt;16 years) and line of treatment as confounding variables. <h3>Results</h3> From a total of 313 patients, 130 (41.5%) use biosimilars therapies, 60.8% of which were women (n= 79). Mean age at diagnosis was 11.2 years (SD= 6.1) and mean age at the start of treatment was 25.1 (SD= 13.4). Patients were classified as oligo/polyarticular JIA (79.2%), JIA related to enthesitis (16.2%) and psoriatic JIA (4.6%). Methotrexate was used in combination in 39.1% of the bsDMARD treatments. The most commonly used drug was Adalimumab (56.8%), followed by Etanercept (28.7%). Table 1 shows incidence rates for adverse events according to severity. For all adverse events, IR is greater in biosimilars compared to original biologic disease modifying antirheumatic drugs (bDMARDs), although the latter have a higher IR of serious adverse events. The IRR was 1.33 (95% CI 1.1-1.6), thus, the risk of adverse events was greater among bsDMARD compared to the original bDMARDs. <h3>Conclusion</h3> The risk of adverse events occurrence is a higher among patients treated with bsDMARD drugs. Although this project allowed us to examine long-term biosimilars safety in JIA, large registries that focus on such patients are needed to better understand rare adverse events. <h3>Reference</h3> [1]Maccora I, et al. OBSIDIAN - real-world evidence of originator to biosimilar drug switch in juvenile idiopathic arthritis. Rheumatology (Oxford) Volume 61, Issue 4, April 2022, Pages 1518–1528 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests:</h3> None declared.